We have sequenced the region encompassing a D beta 2 segment and the J beta 2 segments of the human T-cell antigen receptor beta-chain genes. The D beta 2 element lies about 650 base pairs upstream of a cluster of seven potentially functional J beta 2 sequences and one J beta 2 pseudogene. Examination of human beta-chain cDNA sequences which involve rearranged D beta 2 and J beta 2 elements demonstrates that N-region, as well as junctional, diversity can occur during D-J joining. Further, we present evidence for possible somatic mutation in active J beta 2 segments.